How do waterbugs get their oxygen? (Years 5 and 6)
Lesson plan
Introduction
This series of lessons explores the different
ways waterbugs (macroinvertebrates) obtain
their oxygen. Students observe waterbug
features and draw links between
macroinvertebrate adaptations and water
quality.
Victorian Curriculum F–101 links:
They will recognise that waterbugs obtain their
oxygen in different ways depending on their
type and that this influences where they live in a
waterway. For example, some waterbugs with
gills require highly oxygenated water and thus
need fast-flowing water.
Biological sciences
Activity 1: Waterbug adaptations
Students explore the different ways in which
waterbugs obtain oxygen.
Activity 2: Meet the waterbugs
Students identify the waterbugs in a sample and
draw conclusions about the health of the
waterway from the sensitivities of the waterbugs
found.
Equipment
Levels 5 and 6
Science
Science Understanding
Living things have structural features and
adaptations that help them to survive in their
environment
The growth and survival of living things are
affected by the physical conditions of their
environment
Geography
Geographical Knowledge
Factors that shape places and influence
interconnections
Influence of people, including the influence of
Aboriginal and Torres Strait Islander peoples,
on the environmental characteristics of
Australian places
Environmental and human influences on the
location and characteristics of places and the
management of spaces within them
Waterbug collection equipment: net, pole, bucket and gloves
Waterbug viewing equipment: sorting trays (x5); ice cube trays (x5); spoons (x25);
magnifying glasses
Waterbug sample from a local waterway
3–4 images of waterways
3–4 annotated images of waterbugs explaining how they breathe (attached)
5 x laminated macro-invertebrate identification charts (attached)
Digital microscope and plastic petri dishes (if possible)
Access to a whiteboard.
1
Victorian Curriculum and Assessment Authority (VCAA)
<http://victoriancurriculum.vcaa.vic.edu.au/> Accessed 14 August 2016.
Preparation
Before the lesson, collect a sample of waterbugs from a local creek. After the lesson, make
sure that you take them back to the same place you collected them.
Gather some images of local waterways.
Ensure that all safety requirements are followed.
Activity 1: Waterbug adaptations
Students explore the different ways in which waterbugs obtain oxygen.
Activity steps
1. Introduce the term ‘aquatic macroinvertebrates’. Explain that this refers to the fact that
these animals live in water and have no backbone. It is easier for us to call them
‘waterbugs’. Waterbugs are a collection of bizarre, strange and fascinating creatures that
spend some or all of their lives in waterways. You find them in ponds, streams, estuaries
and irrigation drains. You may even find some in your swimming pool!
2. Ask if anyone has seen waterbugs before and if they know what they were called.
3. Tell students that you have collected a sample of waterbugs for them to learn more
about in today’s lesson.
4. Show the image of the waterway from which you collected the sample. Explain how you
collected the sample. Use the terms riparian vegetation; verge; riffle; aquatic plants;
slow-flowing, deep pools; muddy, sandy or rocky bottom and explain their meaning. A
drawing, diagram or enlarged, laminated photographs of a waterway may be useful.
Display the Scope Waterbugs video [3:13] found on the Melbourne Water website at
<http://www.melbournewater.com.au/getinvolved/protecttheenvironment/Pages/Waterbu
g-Census.aspx> Ask students to suggest which of the new terms could describe the
area that is featured in the video. How did Priya (the narrator) sample for waterbugs?
How did some of the waterbugs breathe underwater?
Waterbugs and oxygen
5. Lead a discussion about the structures waterbugs have to obtain oxygen and how they
function. Use the annotated images of waterbugs to explain the different ways they
obtain their oxygen (refer to Teacher background).
6. Show the images of waterbugs explaining how they breathe. Discuss the structure of
each waterbug and its particular behaviours. Ask students to mime how these waterbugs
breathe.
Teacher background
Macro-invertebrates with gills
Species such as mayfly nymphs have respiratory gills on their abdomen. They generally live
in flowing water and use the flow of water over their gills to ventilate them.
Carrying a water bubble underwater
Some species such as water boatmen breathe air when they are at the surface of the water.
They are able to breathe underwater by carrying an air bubble trapped by the hairs that line
their body.
A snorkel-type structure
With the aid of a breathing tube in their tails, mosquito larvae obtain oxygen from the air.
This is similar to using a snorkel.
Oxygen diffuses through the skin
Freshwater worms get their oxygen from water. The oxygen passes through their body wall
in a process called diffusion.
Breathing air
A water strider is able to stand on the water surface using the water-surface tension and
take in oxygen from the air.
Activity 2: Meet the waterbugs
Students identify the waterbugs in a sample and draw conclusions about the health of the
waterway from the sensitivities of the waterbugs found.
Activity steps
1. Review students learning from the previous activity. Show students the water samples
and explain that they will be looking at the waterbugs.
2. Explain how to look for waterbugs in the sample and how to identify them. Use this
opportunity to demonstrate how to treat creatures ethically i.e. caring for the live
organisms, using spoons for carefully lifting the waterbugs from the sample.
3. Demonstrate how to use equipment correctly. For example:

using the spoon to carefully lift the waterbugs from the sample into the ice cube trays
for observation

using magnifying glasses to look for features on our waterbugs

using the identification charts (with photos) to help identify common waterbugs

not stirring up the sample—it makes it harder to see the waterbugs!
4. Organise students into small groups. Explain that they will be looking for waterbugs in a
tray. Assign the groups a tray to look at.
5. Using the naked eye or magnifying glasses, students to make some observations of the
sample of waterbugs such as:

the number of different types

the numbers of each type

the size, shape, colour of the waterbugs

features such as legs, tail, wings or mouth parts.
If possible, use a computer microscope to view waterbugs using a magnification of 10X.
6. As a class, discuss the waterbugs that were found and explain why a diversity of
waterbugs is important. Using the class data, complete a Macroinvertebrate data form
(download from
<http://www.waterwatchmelbourne.org.au/content/library/Macroinvertebrate_Data_Form.
pdf>
7. Talk about the sensitivity (bug score) of the waterbugs. The higher the bug score, the
more sensitive the organism is to the environmental conditions. If you have a wide
variety of waterbugs including those with a high bug score, it indicates that the waterway
is healthy.
What do the class results indicate about the quality of the waterway in which they
were found?
How did the waterbugs found in the sample obtain their oxygen? What does that
indicate about the quality of the waterway in which they were found?
8. Ask students what kind of actions can they take to help protect their waterways?
Examples include:
Increased nutrients affect water quality. Therefore you need to pick up dog poo when
walking your dog as it enters waterways via stormwater.
Make sure litter goes in the bin as litter can enter waterways via stormwater.
If you like to see a range of animals around your local waterway, do your bit to limit
water pollution.
Look after the small macro-invertebrates and you are looking after the larger animals.
Plant trees to increase shade and oxygen levels.
Extension activity
Present scenarios such as:
A water scientist found large numbers of different macro-invertebrates including mayfly
nymphs, caddis fly larvae and dragonfly nymphs. What might this tell you about the water
quality?
A water scientist found large numbers of several macro-invertebrates such as mosquito
larvae, water boatmen and water striders. What might this tell you about the water quality?
The vegetation along a creek bank is removed and the water turbidity increases. What might
happen to macro-invertebrates with gills?
What larger animals do you expect to find if there is a large variety of macroinvertebrates/low variety of macro-invertebrates?
Key messages
Our waterways support a diverse range of plant and animal life, including native fish, frogs
and platypuses. They are worth looking after.
Everyone can help improve local rivers and creeks by reducing stormwater pollution – simple
things like picking up after your dog, binning rubbish and fixing oil leaks in your car can
reduce the impacts.
Resources
River health at home, Melbourne Water
<http://www.melbournewater.com.au/getinvolved/protecttheenvironment/riverhealthtips/Page
s/River-health-at-home.aspx>
Healthy Waterways Waterwatch, Melbourne Water
<http://www.melbournewater.com.au/getinvolved/protecttheenvironment/Pages/Monitorriver-health.aspx>
Waterbug Census, Melbourne Water
<http://www.melbournewater.com.au/getinvolved/protecttheenvironment/Pages/WaterbugCensus.aspx
Waterbug Guide Online, Melbourne Water
<http://www.melbournewater.com.au/getinvolved/protecttheenvironment/Documents/Waterb
ug%20Guide_Online.pdf>
How waterbugs breathe